The present invention pertains to a hydraulic mount, particularly adapted for automotive powertrain applications, which includes a decoupler member formed of an electroactive polymer whereby the configuration of the decoupler may be modified to modify the dynamic stiffness and damping characteristics of the mount.
Hydraulic type vibration damping mounts have been developed which are particularly adapted for automotive powertrain support applications. One type of hydraulic mount includes a decoupler member which is operable to undergo relatively free limited motion in phase with the input vibrations to the mount to provide low dynamic stiffness of the mount to thereby effectively isolate relatively low amplitude vibrations.
Conventional decoupled hydraulic mounts are normally designed such that the passive decoupler has a resonance frequency in a particular range. Conventional hydraulic mounts with passive decouplers typically resonate in the 100 Hertz to 300 Hertz frequency range, for example, and the dynamic stiffness of the mount increases substantially in frequency ranges above the resonance frequency of the decoupler, since the motion of the decoupler is not able to compensate for the volumetric change of the fluid pumping chamber of the mount. Accordingly, reduced isolation of vibrations above the resonant frequency range of the decoupler is experienced and high frequency engine generated vibrations, for example, are typically transmitted to the vehicle body structure.
The vibration isolation characteristics of a hydraulic mount can be varied by imposing certain forces on the decoupler. For example, an air cushion or air xe2x80x9cspringxe2x80x9d comprising a trapped volume of air between the decoupler and a partition plate can change the damping characteristics of the mount. However, if the motion of the decoupler can be more actively and accurately controlled, the effective dynamic stiffness of the mount can be further reduced at selected frequencies and better isolation characteristics can be obtained for powertrain mounts used in automotive vehicle applications, in particular. For example, it may be desired to control the motion of the decoupler as a function of engine speed (crankshaft revolutions per minute or rpm) such that the vibration isolation characteristics of the mount are achieved in one or more frequency ranges of vibrations related to engine speed and which would be typically input to the mount. It is to these ends that the present invention has been developed.
The present invention provides an improved hydraulic mount, particularly adapted for automotive vehicle engine and related powertrain applications.
In accordance of one important aspect of the invention, a hydraulic engine or powertrain mount is provided which includes an active decoupler and which has a dynamic stiffness which may be substantially lower than the static stiffness of the mount. Moreover, the dynamic stiffness of the mount may be variably xe2x80x9ctunedxe2x80x9d to vehicle engine speed, for example, such that the mount provides good vibration isolation between the engine and the vehicle body.
In accordance with another aspect of the invention, a hydraulic mount with an active decoupler is provided wherein the decoupler shape or motion may be controlled in accordance with a particular vibration disturbance acting on the hydraulic mount. In particular, the decoupler is preferably formed of an electroactive polymer material whose shape and/or volume may be changed as a function of imposing an electric field on the decoupler. Accordingly, the decoupler may be actuated such that it is deflected or moved as a function of the vibrations input to the mount and as a consequence the decoupler may influence the dynamic stiffness characteristics of the mount. The mount may be controlled such that a very low magnitude of mount dynamic stiffness is provided at selected vibration frequencies normally imposed on the mount. Under other operating conditions, such as when the vehicle is in motion or under hard acceleration, the decoupler may be configured such as to force hydraulic fluid in the mount to flow through an orifice or orifice track to provide a higher mount dynamic stiffness and damping characteristics which can be used to control or limit the motion of the vehicle powertrain.
In accordance with yet another aspect of the present invention, an active decoupler hydraulic mount is provided which is operable to satisfy substantially all of the requirements for static stiffness, vibration isolation and dynamic stiffness of the mount for all operating characteristics of a vehicle associated with the mount.